1. Field of the Invention
The present invention relates to the field of thermodynamic heat engines and more particularly to heat engines incorporating a solid state element as the working medium.
2. Description of the Prior Art
Conventional thermodynamic heat engines employ a gas or gas-liquid thermodynamic working medium to drive the engine. By exploiting the solid state joule effect it has also been found possible to devise a thermodynamic heat engine which employs a solid state material as the working medium. The joule effect is based upon a change in physical size of a solid state element with a change in temperature.
There are two principal types of solid state, joule effect, solid state heat engines which have previously been employed. The first type is a turbine type, as shown in Lee, U.S. Pat. No. 3,303,642, wherein the phases of energy addition and removal in the thermodynamic cycle are performed by means of a torque applied to and exerted by a pair of pulleys. The second type is a field type of solid state engine, as shown in Cory, U.S. Pat. No. 4,027,479, wherein the phases of energy addition and removal of the thermodynamic cycle is exchanged in a reaction against a force field. Other types of conventional solid state thermodynamic engines include hydraulic, off-set crank and swash-plate engines which are characterized by the mechanical element which adds or extracts work from the solid state medium.
However, the reliability, efficiency, cost and output performance of each of these prior art solid state engines has been limited and generally restricted from having any practical or commercial applicability. What is needed is an improved solid state engine which overcomes each of these shortcomings of the prior art and by which the efficiency, reliability, and output performance of a solid state engine may be increased to practical levels.